/*
 * Copyright (C) 2011 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.hello.sandbox.core.system.pm;

import java.util.AbstractSet;
import java.util.Iterator;

/**
 * A fast immutable set wrapper for an array that is optimized for non-concurrent iteration. The
 * same iterator instance is reused each time to avoid creating lots of garbage. Iterating over an
 * array in this fashion is 2.5x faster than iterating over a {@link HashSet} so it is worth copying
 * the contents of the set to an array when iterating over it hundreds of times.
 *
 * @hide
 */
public final class FastImmutableArraySet<T> extends AbstractSet<T> {
  FastIterator<T> mIterator;
  T[] mContents;

  public FastImmutableArraySet(T[] contents) {
    mContents = contents;
  }

  @Override
  public Iterator<T> iterator() {
    FastIterator<T> it = mIterator;
    if (it == null) {
      it = new FastIterator<T>(mContents);
      mIterator = it;
    } else {
      it.mIndex = 0;
    }
    return it;
  }

  @Override
  public int size() {
    return mContents.length;
  }

  private static final class FastIterator<T> implements Iterator<T> {
    private final T[] mContents;
    int mIndex;

    public FastIterator(T[] contents) {
      mContents = contents;
    }

    @Override
    public boolean hasNext() {
      return mIndex != mContents.length;
    }

    @Override
    public T next() {
      return mContents[mIndex++];
    }

    @Override
    public void remove() {
      throw new UnsupportedOperationException();
    }
  }
}
